The extinction of the dinosaurs at the end of the Cretaceous period, about 66 million years ago, has long fascinated scientists. While many theories exist, the most widely accepted explanation is the impact of a large asteroid. However, a closer examination of the evidence suggests that massive volcanic activity, specifically the Deccan Traps in India, was the primary driver of the extinction. Three key points support this volcanic hypothesis. First, the Deccan Traps eruptions lasted for over a million years, releasing enormous quantities of sulfur dioxide and carbon dioxide into the atmosphere. These gases would have caused severe acid rain, global cooling followed by warming, and ocean acidification, creating a lethal environment for many species. Second, the timing of the extinctions appears to be gradual rather than sudden. Fossil records show that dinosaur populations were already declining in the million years before the asteroid impact, which aligns with the prolonged stress from volcanic emissions. Third, the asteroid impact theory fails to explain why many species, such as crocodiles and birds, survived despite the catastrophic global winter proposed. In contrast, volcanic activity would have produced a more selective extinction, affecting large terrestrial animals like dinosaurs while sparing smaller and aquatic species that could tolerate changing conditions.
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The reading presents a compelling case for volcanic activity as the main cause of dinosaur extinction, but this argument is flawed. While the Deccan Traps eruptions were indeed massive, their effects were not as severe as the reading suggests. First, the gases released by volcanoes, though significant, were emitted over a long period, allowing the Earth's systems to buffer and recover. In contrast, the asteroid impact released energy equivalent to billions of nuclear bombs, causing an immediate and drastic change in climate. The impact would have ejected dust and aerosols that blocked sunlight for months, halting photosynthesis and collapsing food chains abruptly. Second, the claim of gradual extinction is not supported by recent high-resolution fossil data. Studies of dinosaur fossils in North America show that populations were stable until the very end of the Cretaceous, with no evidence of a prolonged decline. The apparent gradual decline in some regions can be explained by sampling biases or local environmental changes, not global volcanic stress. Third, the survival of crocodiles and birds is not problematic for the impact theory. These animals were smaller, had lower metabolic needs, and could survive on detritus or aquatic food sources that were less affected by the impact winter. In fact, the impact theory better explains the rapid extinction of large dinosaurs and the simultaneous extinction of many marine species, which volcanic activity alone cannot account for.
📝 Hướng dẫn viết Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
📊 TOEFL Integrated Writing Rubric
Content Accuracy: Accurately capture the relationship between lecture and reading
Information Completeness: Cover all key counter-arguments from the lecture
Structure & Coherence: Logical organization and progression
Language Use: Grammar, vocabulary, expression accuracy
Scored 0-30 based on holistic scoring (original 0-5, scaled to 30).
